@inproceedings{h.1939on,
title={On character sums in finite fields},
author={H. Davenport},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203114360829604},
booktitle={Acta Mathematica},
volume={71},
number={1},
pages={99-121},
year={1939},
}